It is often desirable to provide a coupling between the rotating output of a prime mover and the rotating input of a driven load that permits a disparity between the rotational speed of the rotating output of the prime mover and the rotating input of the driven load. For example, in order to permit continuous rotation of the output of the prime mover even when it is desirable to stop rotation of the input of the driven load, it is desirable to provide a coupling that permits the rotational output of the prime mover to continue despite the input of the driven load being stopped.
An example of such a coupling is a torque converter, which provides a hydrodynamic fluid coupling between the rotating output of a prime mover and the rotating input of a driven load. For example, a machine such as a vehicle may include an internal combustion engine and a transmission, with the output of the internal combustion engine coupled to an input of the transmission by the torque converter.
A torque converter generally includes an input coupling for coupling the output of a prime mover to the input of the torque converter, and an output shaft for coupling the output of the torque converter to a driven load, such as a transmission. The torque converter further includes a housing containing fluid, such as hydraulic fluid. Within the housing, the input coupling is coupled to a pump including an impeller for pumping the fluid in the housing. The torque converter further includes a turbine coupled to the output shaft of the torque converter. The impeller of the pump, driven by the input coupling, pumps fluid through the turbine, thereby causing the turbine to rotate and drive the output shaft of the torque converter and the input of, for example, a transmission. By virtue of the fluid coupling provided by the interaction between the impeller and the turbine, the output of the prime mover may continue to rotate the input coupling of the torque converter, even when the output shaft of the torque converter is stopped.
The output shaft of the torque converter extends generally through the center of the impeller and the turbine, which rotate about the longitudinal axis of the output shaft. As a result, it is desirable to provide a fluid seal between the output shaft of the torque converter and the housing of the torque converter to prevent leakage of the fluid from the housing at the interface between the output shaft and the housing. However, such seals are subjected to high levels of stress as a result of rotation of the output shaft relative to the non-rotating portion of the housing. In addition, such seals are subjected to high levels of stress due to high fluid pressure on one side of the seal, resulting from high fluid pressure in the torque converter housing relative to the low pressure on the opposite side of the seal. As a result, such seals may tend to degrade over time, and possibly leak fluid, which is undesirable. Therefore, it may be desirable to develop a seal for a torque converter output shaft that improves the seal at the interface between the output shaft and housing.
One attempt to provide a seal for a torque converter is described in U.S. Pat. No. 6,145,842 to Zellers et al. (“the '842 patent”). The '842 patent discloses a torque converter having a lip seal abutting the torque converter impeller control pump drive hub. The drive hub is rotatably supported in a transmission housing. The '842 patent discloses that oil from the drive hub side of the bushing passes through the bushing into a chamber sealed from atmosphere by the lip seal. The bushing has a control passage for exhausting a portion of the oil from the control pump side prior to reaching the chamber.
Although the lip seal arrangement disclosed in the '842 patent may provide a seal for preventing oil from leaking between the torque converter housing and the impeller control pump drive hub, it may suffer from a number of possible drawbacks. For example, the seal disclosed in the '842 patent does not provide a seal between the torque converter output shaft and the housing of the torque converter. The seal assembly and method disclosed herein may be directed to mitigating or overcoming the possible drawback set forth above.